1. Field of the Invention
The present invention relates to a zoom lens barrel having a plurality of stages of hollow cylindrical units that are extended in an optical axis direction.
2. Description of the Related Art
Conventionally, a lens barrel is configured such that in a wide-angle state, an object-side first lens group is largely extended in an optical axis direction to thereby increase spacing between the first lens group and a second lens group closer to an image-forming surface side than the first lens group is.
Further, the lens barrel is configured such that when zooming is performed from a wide-angle position to a telephoto position, the second lens group is largely extended from the wide-angle position toward an object to thereby reduce the spacing between the first lens group and the second lens group.
Furthermore, the lens barrel is configured such that in a non-shooting state, the first lens group and the second lens group are received (collapsed) into a camera body.
As a lens barrel of the above-mentioned type, there has been known one disclosed in Japanese Patent Laid-Open Publication No. 2005-173412. Parenthesized reference numerals and figure numbers used in the following description denote respective component parts and figures corresponding to those referred to in Japanese Patent Laid-Open Publication No. 2005-173412. The lens barrel disclosed in Japanese Patent Laid-Open Publication No. 2005-173412 includes a first cam member (10) formed with a first cam portion (10a) for driving a first holding member (7) in an optical axis direction and a second cam member (16) formed with a second cam portion (16a) for driving the first cam member in the optical axis direction.
The first holding member holds a first lens unit (1). The first and second cam portions are shaped such that during zooming operation in the whole range between a telephoto end and a wide angle end, the first holding member is driven from one end to the other such that it moves along a track convex toward one side in the optical axis direction.
Further, the lens barrel has a third cam member (17) formed with a third cam portion (17a) for driving a second holding member holding a second lens unit (2) in the optical axis direction.
The first holding member (7) holding the first lens unit (first lens group) (1) is largely extended from the collapsed position (FIG. 1) to the wide-angle position along a combination of respective tracks of a cam grove portion (22a) of a fixed barrel (22), the second cam portion (cam groove portion) (16a) of the second cam member (second cam barrel) (16), and the first cam portion (cam groove portion) (10a) of the first cam member (first cam barrel) (10). Further, the lens barrel is brought into a telephoto state (FIG. 3) where the spacing in the optical axis direction between the first lens group (1) and the second lens group (2) is reduced.
However, in the telephoto state (FIG. 3) where the spacing in the optical axis direction between the first lens group (1) and the second lens group (2) is reduced, the conventional technique disclosed in Japanese Patent Laid-Open Publication No. 2005-173412 suffers from the following problem.
To attain a higher photographing magnification, it is desirable to reduce the spacing between the first lens group and the second lens group in the telephoto state. However, a ring member (12), a guide member (11), and the first cam barrel (10) are located on the object side of a cam follower part (8a) of a second lens holder (8). This makes it impossible to further move the second lens holder (8) toward an object to reduce the spacing between the first lens group (1) and the second lens group (2).